I assure you I wasn't laughing in a mean kind of way - a lot of people who write on forums are very witty and I thought perhaps this was one of those people seeing an opportunity to make a funny post which I liked in any case.

Now that you understand the name of the department stores you'll be able to shop till you drop - sounds like a pretty busy schedule in any case.
Chatuchuk will be very tiring (every time I've been there it's been crowded and hot - half a day is generally enough). Suggest you get there early so you can look at the stalls instead of the backs of everyone else's head and shoulders - it gets that crowded.
If you've had enough of that after half a day, you could always go to Emporium or Central Chitlom on your way back to Siam - as well as good shopping, both of these stores have excellent food courts (and Emporium has an Oriental cafe .... the Mandarin Oriental hotel has a small cafe on the ground floor right by the front entrance... very nice and would be a pleasant time after the rigours of Chatuchuk.

There are lots of market stalls hidden away in the back streets in various places around town - from around noon, they are crowded with locals looking for a bargain during their lunchbreak. There are some up near the palace.